The invention relates to probes used in intra vaginal- and/or intra anal electro-stimulation and bio-feedback training, in particular for registering and training the pelvic floor muscles, the urethral sphincter and the internal and external anal sphincters. Also the probes will be used for the aim of research.
In particular, these probes are used in an inserted position into the vagina or into the rectum, i.e. intravaginal or intra-anal.
Many such a probes are known in practice. One of the first of such probes is the so-called manometric probe, which is used as a perineometer by Kegel and described in AM J. obst Gyneocol. 1948; 65; pages 238-304. Since the introduction of this probe, many electrodes have been developed for intra-vaginal and intra-anal electro stimulation and bio feedback training in the treatment of pelvic floor.
Intravaginal and intra-anal electro stimulation and bio feedback training are used for treatment of urinary urge- and stress incontinence, anal dysfunction, and sexual dysfunction. For optimal treatment, knowledge of the structures that are the main targets in stimulating and bio feedback training is needed.
This knowledge of both the anatomy of the pelvic floor and physiological aspects should result in optimal design of probes. Differences in inter-human anatomy are a challenge. Many of the currently used probes, however, have been developed empirically.
Based on the present knowledge of the inventors, the pelvic floor basically comprises the levator ani and the puborectal muscle. The pelvic floor muscle contraction presumably involves contraction of these two muscles. The levator ani is a muscle active in the process of evacuation. On contraction it facilitates the process of defecation and micturition. In contrast, the puborectal muscle is a muscle active in the process of continence. The puborectal muscle is a vertical lying U-shaped sling embracing the urethra and anal channel. Furthermore, the external anal and urethral sphincters originate in the puborectal muscle. During puborectal muscle contraction, the two sphincters contracts synchronously, resulting in a closure (sealing) of the urethra and anal channel.
Continence, in short, is a result of the direct action of the puborectal muscle per sé and the external anal and urethral sphincters.
In sphincter/stress incontinence, enforcement of the external sphincters, and/or pelvic floor muscles, the puborectal muscle should, according to the inventors, be the main target of electro stimulation. However, the primary targets should not be the muscles but the pelvic and/or pudendal nerve fibres. These fibres directly activated by electro stimulation indirectly induce activity of the muscles.
In urge incontinence, two modes of action are described: stimulation of pudendal nerve afferents, resulting in detrusor inhibition through central reflexes, as well as stimulation of efferents resulting in enhancement of pelvic floor and urethral sphincter musculature tone, inducing detrusor inhibition through the guarding reflex. As these modes of action are quite different, with different targets, it is questionable whether the demands for optimal probes are uniform. It is more likely that various types of probes may be needed for optimal stimulation treatment as well as for bio feedback registration.
Various commercially available probes, positioned according to standard protocol as used in daily practice by pelvic floor physiotherapists, were studied and evaluated.
To investigate the positioning of the anal and vaginal probes, we used the Aloka® SSD 1700 Ultrasound, the power Doppler and the Falcon Ultrasound scanner Type 2101 from Bruel-Kjaer Medical, with transducer type 8658/S and 1850, to localize musculature and the neurovascular bundle of the pelvic floor. The transducer 8658/S was used in combination with the Brachy balloon from Barzell Whitmore Maroon Bells®. The anatomy of the pelvic floor was investigated in detail using the 0.5-T MRI scanner (Philips NT5, Philips Medical Systems®, Best, the Netherlands) equipped with an endoanal coil. We performed a thorough literature review on pelvic floor anatomy and placements of probes in pelvic floor physiotherapy. We evaluated the optimal placement of probes in two healthy multiparous women, without pelvic floor dysfunction. The distance from the recording rings to the muscles is described at the proximal parts of the puborectal muscle and the anal external sphincter. Positioning of the anal probes was examined in left lateral decubitis position, with the ultrasound transducer introduced in the vagina. The positioning of the vaginal probes was examined in lithotomic position with the ultrasound transducer in the anal canal. The anatomy was compared with a vast number of MRI examinations performed with an endoanal coil according to protocol in our institute. During the examination the women were asked to strain and to bear down. Repeated measures were performed on both subjects with a time interval of three weeks. The time elapsed between using each test probe was 15 min and we requested both women to do 10 fast twitch contractions and 5 slow twitch contractions. Five probes, 3 vaginal and 2 anal, were tested and technically described. Three probes have longitudinal recording plates and two have concentric recording plates.
The Neen vaginal probe from Verity Medical Ltd® has a total length of 7.5 cm and a circumference of 10 cm. It has two longitudinal recording plates. The distance between the top of the probe and both recording plates is 1.5 cm. The two recording plates are situated alongside the body of the probe and are 1.5 cm wide and 3.5 cm long. The distance of the base of the probe to both recording plates is 3.0 cm. The probe is inserted into the vagina, up to the ring at the introitus.
The Veriprobe vaginal probe with longitudinal plates from Verity Medical Ltd® has a total length of 8.8 cm and a circumference of 8.2 cm. Two longitudinal rectangle-shaped recording plates are situated alongside the body of the probe and are 2.0 cm wide and 3.5 cm long, and are flush with the body of the probe. The distance between the two recording plates is 2.0 cm. The distance of the recording plate to the top is 1.5 cm, to the bottom 2.1 cm. The external part of the probe is 1.3 cm long. This probe is inserted up to its handle at the introitus.
The EMG 2-ring vaginal probe 2 mm from V.M.P. Bioparc® has two circular recording plates. The total length of this probe is 12.7 cm, the circumference 7.7 cm. The distance from the top ring to the top of the probe is 1.4 cm. The distance between the two rings is 1.8 cm and the width of both rings is 1.0 cm. This probe is inserted up to the thinnest part, at the level of the introitus.
The Neen anal probe, anuform, from Verity Medical Ltd® has a total length of 8.4 cm and a maximal circumference of 7.0 cm. It consists of a body, with two longitudinal recording plates, a neck and an open ring. The recording plates are trapezoid like. The distal side of the recording plate is 0.5 cm wide, the proximal side 1.0 cm. The length of the recording plate is 2.7 cm. The distance between the two recording plates is about 2.0 cm. The distance of the recording plate to the top of the probe is 1.0 cm, to the base 0.5 cm. The length of the ring is 3.0 cm. This probe is inserted with the ring up to the anal verge.
The EMG 2-ring anal probe 2 mm from V.M.P. Bioparc® has two circular recording plates. The probe has a total length of 13.6 cm. The circumference of the top of the probe is 5.0 cm. The distance from the distal recording ring to the top is 1.8 cm. The distance between the two rings is 1.0 cm. The width of both rings is 0.5 cm. The distance from the proximal ring to the next bulge is 1.0 cm. There are three bulges with two gaps of 1.0 cm in between. These bulges are for the purpose of fixation. The distance from the proximal bulge to the base of the probe is 6.0 cm. This probe is inserted with the proximal bulge at the anal verge.
The literature on the topic of type of probes of the current invention is scarce. The commercially available probes studied vary in design, that is in shape and size of the body of the probe and in type of recording electrodes (plates or rings). Notwithstanding, they all have the same purpose: proper placement during treatment of pelvic floor dysfunction. What proper placement means depends on the structures that need to be stimulated or registered (nerves, external sphincters, puborectal muscle, or other pelvic floor muscles). The muscular anatomy can be described as consisting of, roughly speaking, 3 layers of muscles: from caudal to cranial: the anal external sphincter, the puborectal muscle, and the levator group. The results of the measurements of the vaginal electrodes vary from close to the puborectal muscle (Veriprobe) to 6 cm cranial of the puborectal muscle (EMG 2-ring vaginal probe 2 mm). The anal electrodes vary from next to the anal external sphincter, 1 cm caudal of the puborectal muscle (Neen probe, anuform), to 2 cm cranial of the puborectal muscle and 4 cm cranial at the anal external sphincter (EMG probe anal, 2 rings). Measurements were reproducible in each subject and for each probe, independently of the sequence. Readings of the probe were not influenced by the presence or absence of the ultrasound probe in the adjacent orifice. In case of electrostimulation for treatment of urinary urge incontinence, stimulating should be focused on afferent nerve fibers of the plexus pelvicus and the pudendal nerve or, if the guarding reflex is involved as well, as in case of stress incontinence, on the external sphincter and pelvic floor musculature. It is assumed that, in this respect, of all pelvic floor muscles, the puborectal muscle is the most relevant one. Using electrostimulation in cases of fecal incontinence, the focus is on the anal external sphincter as well as on the puborectal muscle. In biofeedback training we aim to record the function of the urethral and anal sphincters and the puborectal muscle. It was found that for biofeedback training a close relation between the electrode plates and the muscle itself is important. However, in cases of electrostimulation of pelvic floor dysfunction (stress and urge incontinence, fecal incontinence, and obstructed defecation), stimulation of afferent and/or efferent nerves is found to be mandatory and not necessarily direct stimulation of the involved muscles. The general requirement to obtain an effect of electrical stimulation, found during our study, is that the intensity of stimulation should be sufficient to elicit impulses in a relevant nerve. The threshold intensity varies inversely with the nerve fiber diameter, the distance between the nerve and the size of the stimulating electrode, and the pulse configuration. All tested probes had a large electrode area. The effect of this is that a relatively large current is needed to elicit an effect, but this is not by itself harmful. If the electrodes are not positioned at the anal external sphincter and/or the puborectal muscle, we assume that in biofeedback training we are in fact registering a composite EMG signal of the total area, not only the pelvic floor, but the sum of all active surrounding muscles as well as the response to intra-abdominal pressure. Based on our findings we conclude that the electrodes of the probes, as we use them now during electrostimulation and biofeedback training in the treatment of pelvic floor dysfunction, are not optimal for the structures we want to stimulate or to register. Observation of the anal positioning of the probe by vaginal ultrasound demonstrated that during an attempt to perform a pelvic floor contraction, the anal external sphincter ‘rolls’ backwards, taking the shape of a ‘drop’. Simultaneously the urethra stretches itself, elongates and is pulled down during contracting the urethral sphincter and the puborectal muscle. In contrast, during straining, the urethra is shortened and moves upwards.
Optimal probe fitting may be even more complex. According to one reference, sex-dependent differences are visible in all three planes. Because of the clear difference in male and female anatomy, different electrodes are needed in the treatment of pelvic floor dysfunction. Ultrasound and MRI imaging demonstrated that the positioning of the electrodes is close to the plexus pelvicus. Besides stimulation of afferent or efferent, motoric nerves, the mode of action of intravaginal stimulation for urge incontinence may also be related to direct stimulation of the bladder wall or the urethra. If we position the electrodes at the anal external sphincter or in the anal canal below the linea dentata, or just behind the vaginal introitus, electrostimulation is far too painful for the patient. Direct stimulation of skin and mucosa, also at lower intensity, is probably the cause of this pain sensation. In case of biofeedback, the optimal position of the probes for stimulation is quite different. In our opinion the ideal probe should be:
1. registering;
                vaginal: the puborectal muscle, the external urethral sphincter;        anal: the puborectal muscle, the anal external sphincter, the levator ani;2. stimulating the structures we want to stimulate: nerves or muscles;3. shaped and sized adapted to the local anatomy (not vice versa);4. comfortable for the patient;5. maintaining its position;6. the reference electrode should be incorporated;7. suitable for sterilization;8. durable;9. containing rings and plates of electrodes.        